Shifting device and gear unit

Abstract

A shifting device for a transmission unit of a vehicle, in particular a vehicle that is driven by muscle force. The transmission unit has a first shaft, which is formed as a hollow shaft, on which a plurality of free gears is mounted. The free gears are in engagement with a corresponding plurality of gearwheels, which are mounted on a second shaft, wherein the free gears are connectable to the first shaft by means of selecting devices. The selecting devices can be actuated by means of a camshaft arranged coaxially in the first shaft, wherein the camshaft is connected to a driving device in order to be rotated relative to the first shaft to actuate the selecting devices.

What is claimed is: 
     
       1. A gear unit for a vehicle that is driven by muscle force, having a first shaft, on which a plurality of first gearwheels is mounted, and a second shaft, on which a plurality of second gearwheels is mounted, wherein each of the second gearwheels is meshed with a respective one of the first gearwheels, wherein the first gearwheels are formed as free gears which can be connected rotationally fixed to the first shaft by means of selecting devices, wherein each of the second gearwheels is connected nonpositively to the second shaft by means of a respective torque limiting clutch, wherein each of the torque limiting clutches connects each of its associated one of the second gearwheels to the second shaft up to a predetermined torque, and wherein the predetermined torque is adjustable individually for each of the second gearwheels. 
     
     
       2. The gear unit as claimed in  claim 1 , wherein each second gearwheel is adapted to slide on the second shaft above the predetermined torque. 
     
     
       3. The gear unit as claimed in  claim 1 , wherein each torque limiting clutch is designed as a friction clutch. 
     
     
       4. The shifting device as claimed in  claim 1 , wherein the selecting devices are designed as selectable freewheels. 
     
     
       5. The shifting device as claimed in  claim 1 , wherein the selecting devices have selector pawls, which can be brought into engagement with internal toothing of the free gears. 
     
     
       6. A gear unit for a vehicle that is driven by muscle force, having a first shaft, on which a plurality of first gearwheels is mounted, and a second shaft, on which a plurality of second gearwheels is mounted, wherein each of the second gearwheels is in engagement with a corresponding one of the first gearwheels and meshed with the corresponding one of the first gearwheels, wherein each of the second gearwheels can be connected nonpositively to the second shaft by means of a torque limiting clutch, wherein each of the torque limiting clutches connects each if its associated one of the second gearwheels to the second shaft up to a predetermined torque, and wherein the first gearwheels are formed as free gears which can be connected rotationally fixed to the first shaft by means of selecting devices. 
     
     
       7. The gear unit as claimed in  claim 6 , wherein each second gearwheel is adapted to slide on the second shaft above a predetermined torque. 
     
     
       8. The gear unit as claimed in  claim 7 , wherein the predetermined torque is adjustable. 
     
     
       9. The gear unit as claimed in  6 , wherein the second gearwheels are formed as free gears which can be connected rotationally fixed to the second shaft by means of torque limiting clutches. 
     
     
       10. The shifting device as claimed in  claim 6 , wherein the selecting devices are designed as selectable freewheels.